<?php
/**
*  Class for parsing Excel formulas
*
*  License Information:
*
*	Spreadsheet_Excel_Writer:  A library for generating Excel Spreadsheets
*	Copyright (c) 2002-2003 Xavier Noguer xnoguer@rezebra.com
*
*	This library is free software; you can redistribute it and/or
*	modify it under the terms of the GNU Lesser General Public
*	License as published by the Free Software Foundation; either
*	version 2.1 of the License, or (at your option) any later version.
*
*	This library is distributed in the hope that it will be useful,
*	but WITHOUT ANY WARRANTY; without even the implied warranty of
*	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*	Lesser General Public License for more details.
*
*	You should have received a copy of the GNU Lesser General Public
*	License along with this library; if not, write to the Free Software
*	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/**
* @const SPREADSHEET_EXCEL_WRITER_ADD token identifier for character "+"
*/
define('SPREADSHEET_EXCEL_WRITER_ADD', "+");

/**
* @const SPREADSHEET_EXCEL_WRITER_SUB token identifier for character "-"
*/
define('SPREADSHEET_EXCEL_WRITER_SUB', "-");

/**
* @const SPREADSHEET_EXCEL_WRITER_MUL token identifier for character "*"
*/
define('SPREADSHEET_EXCEL_WRITER_MUL', "*");

/**
* @const SPREADSHEET_EXCEL_WRITER_DIV token identifier for character "/"
*/
define('SPREADSHEET_EXCEL_WRITER_DIV', "/");

/**
* @const SPREADSHEET_EXCEL_WRITER_OPEN token identifier for character "("
*/
define('SPREADSHEET_EXCEL_WRITER_OPEN', "(");

/**
* @const SPREADSHEET_EXCEL_WRITER_CLOSE token identifier for character ")"
*/
define('SPREADSHEET_EXCEL_WRITER_CLOSE', ")");

/**
* @const SPREADSHEET_EXCEL_WRITER_COMA token identifier for character ","
*/
define('SPREADSHEET_EXCEL_WRITER_COMA', ",");

/**
* @const SPREADSHEET_EXCEL_WRITER_SEMICOLON token identifier for character ";"
*/
define('SPREADSHEET_EXCEL_WRITER_SEMICOLON', ";");

/**
* @const SPREADSHEET_EXCEL_WRITER_GT token identifier for character ">"
*/
define('SPREADSHEET_EXCEL_WRITER_GT', ">");

/**
* @const SPREADSHEET_EXCEL_WRITER_LT token identifier for character "<"
*/
define('SPREADSHEET_EXCEL_WRITER_LT', "<");

/**
* @const SPREADSHEET_EXCEL_WRITER_LE token identifier for character "<="
*/
define('SPREADSHEET_EXCEL_WRITER_LE', "<=");

/**
* @const SPREADSHEET_EXCEL_WRITER_GE token identifier for character ">="
*/
define('SPREADSHEET_EXCEL_WRITER_GE', ">=");

/**
* @const SPREADSHEET_EXCEL_WRITER_EQ token identifier for character "="
*/
define('SPREADSHEET_EXCEL_WRITER_EQ', "=");

/**
* @const SPREADSHEET_EXCEL_WRITER_NE token identifier for character "<>"
*/
define('SPREADSHEET_EXCEL_WRITER_NE', "<>");


require_once 'PEAR.php';

/**
* Class for parsing Excel formulas
*
* @author   Xavier Noguer <xnoguer@rezebra.com>
* @category FileFormats
* @package  Spreadsheet_Excel_Writer
*/

class Spreadsheet_Excel_Writer_Parser extends PEAR
{
	/**
	* The index of the character we are currently looking at
	* @var integer
	*/
	var $_current_char;

	/**
	* The token we are working on.
	* @var string
	*/
	var $_current_token;

	/**
	* The formula to parse
	* @var string
	*/
	var $_formula;

	/**
	* The character ahead of the current char
	* @var string
	*/
	var $_lookahead;

	/**
	* The parse tree to be generated
	* @var string
	*/
	var $_parse_tree;

	/**
	* The byte order. 1 => big endian, 0 => little endian.
	* @var integer
	*/
	var $_byte_order;

	/**
	* Array of external sheets
	* @var array
	*/
	var $_ext_sheets;

	/**
	* Array of sheet references in the form of REF structures
	* @var array
	*/
	var $_references;

	/**
	* The BIFF version for the workbook
	* @var integer
	*/
	var $_BIFF_version;

	/**
	* The class constructor
	*
	* @param integer $byte_order The byte order (Little endian or Big endian) of the architecture
								 (optional). 1 => big endian, 0 (default) little endian.
	*/
	function Spreadsheet_Excel_Writer_Parser($byte_order, $biff_version)
	{
		$this->_current_char  = 0;
		$this->_BIFF_version  = $biff_version;
		$this->_current_token = '';	   // The token we are working on.
		$this->_formula	   = '';	   // The formula to parse.
		$this->_lookahead	 = '';	   // The character ahead of the current char.
		$this->_parse_tree	= '';	   // The parse tree to be generated.
		$this->_initializeHashes();	  // Initialize the hashes: ptg's and function's ptg's
		$this->_byte_order = $byte_order; // Little Endian or Big Endian
		$this->_ext_sheets = array();
		$this->_references = array();
	}

	/**
	* Initialize the ptg and function hashes.
	*
	* @access private
	*/
	function _initializeHashes()
	{
		// The Excel ptg indices
		$this->ptg = array(
			'ptgExp'	   => 0x01,
			'ptgTbl'	   => 0x02,
			'ptgAdd'	   => 0x03,
			'ptgSub'	   => 0x04,
			'ptgMul'	   => 0x05,
			'ptgDiv'	   => 0x06,
			'ptgPower'	 => 0x07,
			'ptgConcat'	=> 0x08,
			'ptgLT'		=> 0x09,
			'ptgLE'		=> 0x0A,
			'ptgEQ'		=> 0x0B,
			'ptgGE'		=> 0x0C,
			'ptgGT'		=> 0x0D,
			'ptgNE'		=> 0x0E,
			'ptgIsect'	 => 0x0F,
			'ptgUnion'	 => 0x10,
			'ptgRange'	 => 0x11,
			'ptgUplus'	 => 0x12,
			'ptgUminus'	=> 0x13,
			'ptgPercent'   => 0x14,
			'ptgParen'	 => 0x15,
			'ptgMissArg'   => 0x16,
			'ptgStr'	   => 0x17,
			'ptgAttr'	  => 0x19,
			'ptgSheet'	 => 0x1A,
			'ptgEndSheet'  => 0x1B,
			'ptgErr'	   => 0x1C,
			'ptgBool'	  => 0x1D,
			'ptgInt'	   => 0x1E,
			'ptgNum'	   => 0x1F,
			'ptgArray'	 => 0x20,
			'ptgFunc'	  => 0x21,
			'ptgFuncVar'   => 0x22,
			'ptgName'	  => 0x23,
			'ptgRef'	   => 0x24,
			'ptgArea'	  => 0x25,
			'ptgMemArea'   => 0x26,
			'ptgMemErr'	=> 0x27,
			'ptgMemNoMem'  => 0x28,
			'ptgMemFunc'   => 0x29,
			'ptgRefErr'	=> 0x2A,
			'ptgAreaErr'   => 0x2B,
			'ptgRefN'	  => 0x2C,
			'ptgAreaN'	 => 0x2D,
			'ptgMemAreaN'  => 0x2E,
			'ptgMemNoMemN' => 0x2F,
			'ptgNameX'	 => 0x39,
			'ptgRef3d'	 => 0x3A,
			'ptgArea3d'	=> 0x3B,
			'ptgRefErr3d'  => 0x3C,
			'ptgAreaErr3d' => 0x3D,
			'ptgArrayV'	=> 0x40,
			'ptgFuncV'	 => 0x41,
			'ptgFuncVarV'  => 0x42,
			'ptgNameV'	 => 0x43,
			'ptgRefV'	  => 0x44,
			'ptgAreaV'	 => 0x45,
			'ptgMemAreaV'  => 0x46,
			'ptgMemErrV'   => 0x47,
			'ptgMemNoMemV' => 0x48,
			'ptgMemFuncV'  => 0x49,
			'ptgRefErrV'   => 0x4A,
			'ptgAreaErrV'  => 0x4B,
			'ptgRefNV'	 => 0x4C,
			'ptgAreaNV'	=> 0x4D,
			'ptgMemAreaNV' => 0x4E,
			'ptgMemNoMemN' => 0x4F,
			'ptgFuncCEV'   => 0x58,
			'ptgNameXV'	=> 0x59,
			'ptgRef3dV'	=> 0x5A,
			'ptgArea3dV'   => 0x5B,
			'ptgRefErr3dV' => 0x5C,
			'ptgAreaErr3d' => 0x5D,
			'ptgArrayA'	=> 0x60,
			'ptgFuncA'	 => 0x61,
			'ptgFuncVarA'  => 0x62,
			'ptgNameA'	 => 0x63,
			'ptgRefA'	  => 0x64,
			'ptgAreaA'	 => 0x65,
			'ptgMemAreaA'  => 0x66,
			'ptgMemErrA'   => 0x67,
			'ptgMemNoMemA' => 0x68,
			'ptgMemFuncA'  => 0x69,
			'ptgRefErrA'   => 0x6A,
			'ptgAreaErrA'  => 0x6B,
			'ptgRefNA'	 => 0x6C,
			'ptgAreaNA'	=> 0x6D,
			'ptgMemAreaNA' => 0x6E,
			'ptgMemNoMemN' => 0x6F,
			'ptgFuncCEA'   => 0x78,
			'ptgNameXA'	=> 0x79,
			'ptgRef3dA'	=> 0x7A,
			'ptgArea3dA'   => 0x7B,
			'ptgRefErr3dA' => 0x7C,
			'ptgAreaErr3d' => 0x7D
			);

		// Thanks to Michael Meeks and Gnumeric for the initial arg values.
		//
		// The following hash was generated by "function_locale.pl" in the distro.
		// Refer to function_locale.pl for non-English function names.
		//
		// The array elements are as follow:
		// ptg:   The Excel function ptg code.
		// args:  The number of arguments that the function takes:
		//		   >=0 is a fixed number of arguments.
		//		   -1  is a variable  number of arguments.
		// class: The reference, value or array class of the function args.
		// vol:   The function is volatile.
		//
		$this->_functions = array(
			  // function				  ptg  args  class  vol
			  'COUNT'		   => array(   0,   -1,	0,	0 ),
			  'IF'			  => array(   1,   -1,	1,	0 ),
			  'ISNA'			=> array(   2,	1,	1,	0 ),
			  'ISERROR'		 => array(   3,	1,	1,	0 ),
			  'SUM'			 => array(   4,   -1,	0,	0 ),
			  'AVERAGE'		 => array(   5,   -1,	0,	0 ),
			  'MIN'			 => array(   6,   -1,	0,	0 ),
			  'MAX'			 => array(   7,   -1,	0,	0 ),
			  'ROW'			 => array(   8,   -1,	0,	0 ),
			  'COLUMN'		  => array(   9,   -1,	0,	0 ),
			  'NA'			  => array(  10,	0,	0,	0 ),
			  'NPV'			 => array(  11,   -1,	1,	0 ),
			  'STDEV'		   => array(  12,   -1,	0,	0 ),
			  'DOLLAR'		  => array(  13,   -1,	1,	0 ),
			  'FIXED'		   => array(  14,   -1,	1,	0 ),
			  'SIN'			 => array(  15,	1,	1,	0 ),
			  'COS'			 => array(  16,	1,	1,	0 ),
			  'TAN'			 => array(  17,	1,	1,	0 ),
			  'ATAN'			=> array(  18,	1,	1,	0 ),
			  'PI'			  => array(  19,	0,	1,	0 ),
			  'SQRT'			=> array(  20,	1,	1,	0 ),
			  'EXP'			 => array(  21,	1,	1,	0 ),
			  'LN'			  => array(  22,	1,	1,	0 ),
			  'LOG10'		   => array(  23,	1,	1,	0 ),
			  'ABS'			 => array(  24,	1,	1,	0 ),
			  'INT'			 => array(  25,	1,	1,	0 ),
			  'SIGN'			=> array(  26,	1,	1,	0 ),
			  'ROUND'		   => array(  27,	2,	1,	0 ),
			  'LOOKUP'		  => array(  28,   -1,	0,	0 ),
			  'INDEX'		   => array(  29,   -1,	0,	1 ),
			  'REPT'			=> array(  30,	2,	1,	0 ),
			  'MID'			 => array(  31,	3,	1,	0 ),
			  'LEN'			 => array(  32,	1,	1,	0 ),
			  'VALUE'		   => array(  33,	1,	1,	0 ),
			  'TRUE'			=> array(  34,	0,	1,	0 ),
			  'FALSE'		   => array(  35,	0,	1,	0 ),
			  'AND'			 => array(  36,   -1,	0,	0 ),
			  'OR'			  => array(  37,   -1,	0,	0 ),
			  'NOT'			 => array(  38,	1,	1,	0 ),
			  'MOD'			 => array(  39,	2,	1,	0 ),
			  'DCOUNT'		  => array(  40,	3,	0,	0 ),
			  'DSUM'			=> array(  41,	3,	0,	0 ),
			  'DAVERAGE'		=> array(  42,	3,	0,	0 ),
			  'DMIN'			=> array(  43,	3,	0,	0 ),
			  'DMAX'			=> array(  44,	3,	0,	0 ),
			  'DSTDEV'		  => array(  45,	3,	0,	0 ),
			  'VAR'			 => array(  46,   -1,	0,	0 ),
			  'DVAR'			=> array(  47,	3,	0,	0 ),
			  'TEXT'			=> array(  48,	2,	1,	0 ),
			  'LINEST'		  => array(  49,   -1,	0,	0 ),
			  'TREND'		   => array(  50,   -1,	0,	0 ),
			  'LOGEST'		  => array(  51,   -1,	0,	0 ),
			  'GROWTH'		  => array(  52,   -1,	0,	0 ),
			  'PV'			  => array(  56,   -1,	1,	0 ),
			  'FV'			  => array(  57,   -1,	1,	0 ),
			  'NPER'			=> array(  58,   -1,	1,	0 ),
			  'PMT'			 => array(  59,   -1,	1,	0 ),
			  'RATE'			=> array(  60,   -1,	1,	0 ),
			  'MIRR'			=> array(  61,	3,	0,	0 ),
			  'IRR'			 => array(  62,   -1,	0,	0 ),
			  'RAND'			=> array(  63,	0,	1,	1 ),
			  'MATCH'		   => array(  64,   -1,	0,	0 ),
			  'DATE'			=> array(  65,	3,	1,	0 ),
			  'TIME'			=> array(  66,	3,	1,	0 ),
			  'DAY'			 => array(  67,	1,	1,	0 ),
			  'MONTH'		   => array(  68,	1,	1,	0 ),
			  'YEAR'			=> array(  69,	1,	1,	0 ),
			  'WEEKDAY'		 => array(  70,   -1,	1,	0 ),
			  'HOUR'			=> array(  71,	1,	1,	0 ),
			  'MINUTE'		  => array(  72,	1,	1,	0 ),
			  'SECOND'		  => array(  73,	1,	1,	0 ),
			  'NOW'			 => array(  74,	0,	1,	1 ),
			  'AREAS'		   => array(  75,	1,	0,	1 ),
			  'ROWS'			=> array(  76,	1,	0,	1 ),
			  'COLUMNS'		 => array(  77,	1,	0,	1 ),
			  'OFFSET'		  => array(  78,   -1,	0,	1 ),
			  'SEARCH'		  => array(  82,   -1,	1,	0 ),
			  'TRANSPOSE'	   => array(  83,	1,	1,	0 ),
			  'TYPE'			=> array(  86,	1,	1,	0 ),
			  'ATAN2'		   => array(  97,	2,	1,	0 ),
			  'ASIN'			=> array(  98,	1,	1,	0 ),
			  'ACOS'			=> array(  99,	1,	1,	0 ),
			  'CHOOSE'		  => array( 100,   -1,	1,	0 ),
			  'HLOOKUP'		 => array( 101,   -1,	0,	0 ),
			  'VLOOKUP'		 => array( 102,   -1,	0,	0 ),
			  'ISREF'		   => array( 105,	1,	0,	0 ),
			  'LOG'			 => array( 109,   -1,	1,	0 ),
			  'CHAR'			=> array( 111,	1,	1,	0 ),
			  'LOWER'		   => array( 112,	1,	1,	0 ),
			  'UPPER'		   => array( 113,	1,	1,	0 ),
			  'PROPER'		  => array( 114,	1,	1,	0 ),
			  'LEFT'			=> array( 115,   -1,	1,	0 ),
			  'RIGHT'		   => array( 116,   -1,	1,	0 ),
			  'EXACT'		   => array( 117,	2,	1,	0 ),
			  'TRIM'			=> array( 118,	1,	1,	0 ),
			  'REPLACE'		 => array( 119,	4,	1,	0 ),
			  'SUBSTITUTE'	  => array( 120,   -1,	1,	0 ),
			  'CODE'			=> array( 121,	1,	1,	0 ),
			  'FIND'			=> array( 124,   -1,	1,	0 ),
			  'CELL'			=> array( 125,   -1,	0,	1 ),
			  'ISERR'		   => array( 126,	1,	1,	0 ),
			  'ISTEXT'		  => array( 127,	1,	1,	0 ),
			  'ISNUMBER'		=> array( 128,	1,	1,	0 ),
			  'ISBLANK'		 => array( 129,	1,	1,	0 ),
			  'T'			   => array( 130,	1,	0,	0 ),
			  'N'			   => array( 131,	1,	0,	0 ),
			  'DATEVALUE'	   => array( 140,	1,	1,	0 ),
			  'TIMEVALUE'	   => array( 141,	1,	1,	0 ),
			  'SLN'			 => array( 142,	3,	1,	0 ),
			  'SYD'			 => array( 143,	4,	1,	0 ),
			  'DDB'			 => array( 144,   -1,	1,	0 ),
			  'INDIRECT'		=> array( 148,   -1,	1,	1 ),
			  'CALL'			=> array( 150,   -1,	1,	0 ),
			  'CLEAN'		   => array( 162,	1,	1,	0 ),
			  'MDETERM'		 => array( 163,	1,	2,	0 ),
			  'MINVERSE'		=> array( 164,	1,	2,	0 ),
			  'MMULT'		   => array( 165,	2,	2,	0 ),
			  'IPMT'			=> array( 167,   -1,	1,	0 ),
			  'PPMT'			=> array( 168,   -1,	1,	0 ),
			  'COUNTA'		  => array( 169,   -1,	0,	0 ),
			  'PRODUCT'		 => array( 183,   -1,	0,	0 ),
			  'FACT'			=> array( 184,	1,	1,	0 ),
			  'DPRODUCT'		=> array( 189,	3,	0,	0 ),
			  'ISNONTEXT'	   => array( 190,	1,	1,	0 ),
			  'STDEVP'		  => array( 193,   -1,	0,	0 ),
			  'VARP'			=> array( 194,   -1,	0,	0 ),
			  'DSTDEVP'		 => array( 195,	3,	0,	0 ),
			  'DVARP'		   => array( 196,	3,	0,	0 ),
			  'TRUNC'		   => array( 197,   -1,	1,	0 ),
			  'ISLOGICAL'	   => array( 198,	1,	1,	0 ),
			  'DCOUNTA'		 => array( 199,	3,	0,	0 ),
			  'ROUNDUP'		 => array( 212,	2,	1,	0 ),
			  'ROUNDDOWN'	   => array( 213,	2,	1,	0 ),
			  'RANK'			=> array( 216,   -1,	0,	0 ),
			  'ADDRESS'		 => array( 219,   -1,	1,	0 ),
			  'DAYS360'		 => array( 220,   -1,	1,	0 ),
			  'TODAY'		   => array( 221,	0,	1,	1 ),
			  'VDB'			 => array( 222,   -1,	1,	0 ),
			  'MEDIAN'		  => array( 227,   -1,	0,	0 ),
			  'SUMPRODUCT'	  => array( 228,   -1,	2,	0 ),
			  'SINH'			=> array( 229,	1,	1,	0 ),
			  'COSH'			=> array( 230,	1,	1,	0 ),
			  'TANH'			=> array( 231,	1,	1,	0 ),
			  'ASINH'		   => array( 232,	1,	1,	0 ),
			  'ACOSH'		   => array( 233,	1,	1,	0 ),
			  'ATANH'		   => array( 234,	1,	1,	0 ),
			  'DGET'			=> array( 235,	3,	0,	0 ),
			  'INFO'			=> array( 244,	1,	1,	1 ),
			  'DB'			  => array( 247,   -1,	1,	0 ),
			  'FREQUENCY'	   => array( 252,	2,	0,	0 ),
			  'ERROR.TYPE'	  => array( 261,	1,	1,	0 ),
			  'REGISTER.ID'	 => array( 267,   -1,	1,	0 ),
			  'AVEDEV'		  => array( 269,   -1,	0,	0 ),
			  'BETADIST'		=> array( 270,   -1,	1,	0 ),
			  'GAMMALN'		 => array( 271,	1,	1,	0 ),
			  'BETAINV'		 => array( 272,   -1,	1,	0 ),
			  'BINOMDIST'	   => array( 273,	4,	1,	0 ),
			  'CHIDIST'		 => array( 274,	2,	1,	0 ),
			  'CHIINV'		  => array( 275,	2,	1,	0 ),
			  'COMBIN'		  => array( 276,	2,	1,	0 ),
			  'CONFIDENCE'	  => array( 277,	3,	1,	0 ),
			  'CRITBINOM'	   => array( 278,	3,	1,	0 ),
			  'EVEN'			=> array( 279,	1,	1,	0 ),
			  'EXPONDIST'	   => array( 280,	3,	1,	0 ),
			  'FDIST'		   => array( 281,	3,	1,	0 ),
			  'FINV'			=> array( 282,	3,	1,	0 ),
			  'FISHER'		  => array( 283,	1,	1,	0 ),
			  'FISHERINV'	   => array( 284,	1,	1,	0 ),
			  'FLOOR'		   => array( 285,	2,	1,	0 ),
			  'GAMMADIST'	   => array( 286,	4,	1,	0 ),
			  'GAMMAINV'		=> array( 287,	3,	1,	0 ),
			  'CEILING'		 => array( 288,	2,	1,	0 ),
			  'HYPGEOMDIST'	 => array( 289,	4,	1,	0 ),
			  'LOGNORMDIST'	 => array( 290,	3,	1,	0 ),
			  'LOGINV'		  => array( 291,	3,	1,	0 ),
			  'NEGBINOMDIST'	=> array( 292,	3,	1,	0 ),
			  'NORMDIST'		=> array( 293,	4,	1,	0 ),
			  'NORMSDIST'	   => array( 294,	1,	1,	0 ),
			  'NORMINV'		 => array( 295,	3,	1,	0 ),
			  'NORMSINV'		=> array( 296,	1,	1,	0 ),
			  'STANDARDIZE'	 => array( 297,	3,	1,	0 ),
			  'ODD'			 => array( 298,	1,	1,	0 ),
			  'PERMUT'		  => array( 299,	2,	1,	0 ),
			  'POISSON'		 => array( 300,	3,	1,	0 ),
			  'TDIST'		   => array( 301,	3,	1,	0 ),
			  'WEIBULL'		 => array( 302,	4,	1,	0 ),
			  'SUMXMY2'		 => array( 303,	2,	2,	0 ),
			  'SUMX2MY2'		=> array( 304,	2,	2,	0 ),
			  'SUMX2PY2'		=> array( 305,	2,	2,	0 ),
			  'CHITEST'		 => array( 306,	2,	2,	0 ),
			  'CORREL'		  => array( 307,	2,	2,	0 ),
			  'COVAR'		   => array( 308,	2,	2,	0 ),
			  'FORECAST'		=> array( 309,	3,	2,	0 ),
			  'FTEST'		   => array( 310,	2,	2,	0 ),
			  'INTERCEPT'	   => array( 311,	2,	2,	0 ),
			  'PEARSON'		 => array( 312,	2,	2,	0 ),
			  'RSQ'			 => array( 313,	2,	2,	0 ),
			  'STEYX'		   => array( 314,	2,	2,	0 ),
			  'SLOPE'		   => array( 315,	2,	2,	0 ),
			  'TTEST'		   => array( 316,	4,	2,	0 ),
			  'PROB'			=> array( 317,   -1,	2,	0 ),
			  'DEVSQ'		   => array( 318,   -1,	0,	0 ),
			  'GEOMEAN'		 => array( 319,   -1,	0,	0 ),
			  'HARMEAN'		 => array( 320,   -1,	0,	0 ),
			  'SUMSQ'		   => array( 321,   -1,	0,	0 ),
			  'KURT'			=> array( 322,   -1,	0,	0 ),
			  'SKEW'			=> array( 323,   -1,	0,	0 ),
			  'ZTEST'		   => array( 324,   -1,	0,	0 ),
			  'LARGE'		   => array( 325,	2,	0,	0 ),
			  'SMALL'		   => array( 326,	2,	0,	0 ),
			  'QUARTILE'		=> array( 327,	2,	0,	0 ),
			  'PERCENTILE'	  => array( 328,	2,	0,	0 ),
			  'PERCENTRANK'	 => array( 329,   -1,	0,	0 ),
			  'MODE'			=> array( 330,   -1,	2,	0 ),
			  'TRIMMEAN'		=> array( 331,	2,	0,	0 ),
			  'TINV'			=> array( 332,	2,	1,	0 ),
			  'CONCATENATE'	 => array( 336,   -1,	1,	0 ),
			  'POWER'		   => array( 337,	2,	1,	0 ),
			  'RADIANS'		 => array( 342,	1,	1,	0 ),
			  'DEGREES'		 => array( 343,	1,	1,	0 ),
			  'SUBTOTAL'		=> array( 344,   -1,	0,	0 ),
			  'SUMIF'		   => array( 345,   -1,	0,	0 ),
			  'COUNTIF'		 => array( 346,	2,	0,	0 ),
			  'COUNTBLANK'	  => array( 347,	1,	0,	0 ),
			  'ROMAN'		   => array( 354,   -1,	1,	0 )
			  );
	}

	/**
	* Convert a token to the proper ptg value.
	*
	* @access private
	* @param mixed $token The token to convert.
	* @return mixed the converted token on success. PEAR_Error if the token
	*			   is not recognized
	*/
	function _convert($token)
	{
		if (preg_match("/^\"[^\"]{0,255}\"$/", $token)) {
			return $this->_convertString($token);

		} elseif (is_numeric($token)) {
			return $this->_convertNumber($token);

		// match references like A1 or $A$1
		} elseif (preg_match('/^\$?([A-Ia-i]?[A-Za-z])\$?(\d+)$/',$token)) {
			return $this->_convertRef2d($token);

		// match external references like Sheet1!A1 or Sheet1:Sheet2!A1
		} elseif (preg_match("/^\w+(\:\w+)?\![A-Ia-i]?[A-Za-z](\d+)$/u",$token)) {
			return $this->_convertRef3d($token);

		// match external references like 'Sheet1'!A1 or 'Sheet1:Sheet2'!A1
		} elseif (preg_match("/^'[\w -]+(\:[\w -]+)?'\![A-Ia-i]?[A-Za-z](\d+)$/u",$token)) {
			return $this->_convertRef3d($token);

		// match ranges like A1:B2
		} elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)\:(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)$/",$token)) {
			return $this->_convertRange2d($token);

		// match ranges like A1..B2
		} elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)\.\.(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)$/",$token)) {
			return $this->_convertRange2d($token);

		// match external ranges like Sheet1!A1 or Sheet1:Sheet2!A1:B2
		} elseif (preg_match("/^\w+(\:\w+)?\!([A-Ia-i]?[A-Za-z])?(\d+)\:([A-Ia-i]?[A-Za-z])?(\d+)$/u",$token)) {
			return $this->_convertRange3d($token);

		// match external ranges like 'Sheet1'!A1 or 'Sheet1:Sheet2'!A1:B2
		} elseif (preg_match("/^'[\w -]+(\:[\w -]+)?'\!([A-Ia-i]?[A-Za-z])?(\d+)\:([A-Ia-i]?[A-Za-z])?(\d+)$/u",$token)) {
			return $this->_convertRange3d($token);

		// operators (including parentheses)
		} elseif (isset($this->ptg[$token])) {
			return pack("C", $this->ptg[$token]);

		// commented so argument number can be processed correctly. See toReversePolish().
		/*elseif (preg_match("/[A-Z0-9\xc0-\xdc\.]+/",$token))
		{
			return($this->_convertFunction($token,$this->_func_args));
		}*/

		// if it's an argument, ignore the token (the argument remains)
		} elseif ($token == 'arg') {
			return '';
		}
		// TODO: use real error codes
		return $this->raiseError("Unknown token $token");
	}

	/**
	* Convert a number token to ptgInt or ptgNum
	*
	* @access private
	* @param mixed $num an integer or double for conversion to its ptg value
	*/
	function _convertNumber($num)
	{
		// Integer in the range 0..2**16-1
		if ((preg_match("/^\d+$/", $num)) and ($num <= 65535)) {
			return pack("Cv", $this->ptg['ptgInt'], $num);
		} else { // A float
			if ($this->_byte_order) { // if it's Big Endian
				$num = strrev($num);
			}
			return pack("Cd", $this->ptg['ptgNum'], $num);
		}
	}

	/**
	* Convert a string token to ptgStr
	*
	* @access private
	* @param string $string A string for conversion to its ptg value.
	* @return mixed the converted token on success. PEAR_Error if the string
	*			   is longer than 255 characters.
	*/
	function _convertString($string)
	{
		// chop away beggining and ending quotes
		$string = substr($string, 1, strlen($string) - 2);
		if (strlen($string) > 255) {
			return $this->raiseError("String is too long");
		}

		if ($this->_BIFF_version == 0x0500) {
			return pack("CC", $this->ptg['ptgStr'], strlen($string)).$string;
		} elseif ($this->_BIFF_version == 0x0600) {
			$encoding = 0;   // TODO: Unicode support
			return pack("CCC", $this->ptg['ptgStr'], strlen($string), $encoding).$string;
		}
	}

	/**
	* Convert a function to a ptgFunc or ptgFuncVarV depending on the number of
	* args that it takes.
	*
	* @access private
	* @param string  $token	The name of the function for convertion to ptg value.
	* @param integer $num_args The number of arguments the function receives.
	* @return string The packed ptg for the function
	*/
	function _convertFunction($token, $num_args)
	{
		$args	 = $this->_functions[$token][1];
		$volatile = $this->_functions[$token][3];

		// Fixed number of args eg. TIME($i,$j,$k).
		if ($args >= 0) {
			return pack("Cv", $this->ptg['ptgFuncV'], $this->_functions[$token][0]);
		}
		// Variable number of args eg. SUM($i,$j,$k, ..).
		if ($args == -1) {
			return pack("CCv", $this->ptg['ptgFuncVarV'], $num_args, $this->_functions[$token][0]);
		}
	}

	/**
	* Convert an Excel range such as A1:D4 to a ptgRefV.
	*
	* @access private
	* @param string $range An Excel range in the A1:A2 or A1..A2 format.
	*/
	function _convertRange2d($range)
	{
		$class = 2; // as far as I know, this is magick.

		// Split the range into 2 cell refs
		if (preg_match("/^([A-Ia-i]?[A-Za-z])(\d+)\:([A-Ia-i]?[A-Za-z])(\d+)$/", $range)) {
			list($cell1, $cell2) = split(':', $range);
		} elseif (preg_match("/^([A-Ia-i]?[A-Za-z])(\d+)\.\.([A-Ia-i]?[A-Za-z])(\d+)$/", $range)) {
			list($cell1, $cell2) = split('\.\.', $range);

		} else {
			// TODO: use real error codes
			return $this->raiseError("Unknown range separator", 0, PEAR_ERROR_DIE);
		}

		// Convert the cell references
		$cell_array1 = $this->_cellToPackedRowcol($cell1);
		if (PEAR::isError($cell_array1)) {
			return $cell_array1;
		}
		list($row1, $col1) = $cell_array1;
		$cell_array2 = $this->_cellToPackedRowcol($cell2);
		if (PEAR::isError($cell_array2)) {
			return $cell_array2;
		}
		list($row2, $col2) = $cell_array2;

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgArea = pack("C", $this->ptg['ptgArea']);
		} elseif ($class == 1) {
			$ptgArea = pack("C", $this->ptg['ptgAreaV']);
		} elseif ($class == 2) {
			$ptgArea = pack("C", $this->ptg['ptgAreaA']);
		} else {
			// TODO: use real error codes
			return $this->raiseError("Unknown class $class", 0, PEAR_ERROR_DIE);
		}
		return $ptgArea . $row1 . $row2 . $col1. $col2;
	}

	/**
	* Convert an Excel 3d range such as "Sheet1!A1:D4" or "Sheet1:Sheet2!A1:D4" to
	* a ptgArea3d.
	*
	* @access private
	* @param string $token An Excel range in the Sheet1!A1:A2 format.
	* @return mixed The packed ptgArea3d token on success, PEAR_Error on failure.
	*/
	function _convertRange3d($token)
	{
		$class = 2; // as far as I know, this is magick.

		// Split the ref at the ! symbol
		list($ext_ref, $range) = split('!', $token);

		// Convert the external reference part (different for BIFF8)
		if ($this->_BIFF_version == 0x0500) {
			$ext_ref = $this->_packExtRef($ext_ref);
			if (PEAR::isError($ext_ref)) {
				return $ext_ref;
			}
		} elseif ($this->_BIFF_version == 0x0600) {
			 $ext_ref = $this->_getRefIndex($ext_ref);
			 if (PEAR::isError($ext_ref)) {
				 return $ext_ref;
			 }
		}

		// Split the range into 2 cell refs
		list($cell1, $cell2) = split(':', $range);

		// Convert the cell references
		if (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)$/", $cell1)) {
			$cell_array1 = $this->_cellToPackedRowcol($cell1);
			if (PEAR::isError($cell_array1)) {
				return $cell_array1;
			}
			list($row1, $col1) = $cell_array1;
			$cell_array2 = $this->_cellToPackedRowcol($cell2);
			if (PEAR::isError($cell_array2)) {
				return $cell_array2;
			}
			list($row2, $col2) = $cell_array2;
		} else { // It's a rows range (like 26:27)
			 $cells_array = $this->_rangeToPackedRange($cell1.':'.$cell2);
			 if (PEAR::isError($cells_array)) {
				 return $cells_array;
			 }
			 list($row1, $col1, $row2, $col2) = $cells_array;
		}

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgArea = pack("C", $this->ptg['ptgArea3d']);
		} elseif ($class == 1) {
			$ptgArea = pack("C", $this->ptg['ptgArea3dV']);
		} elseif ($class == 2) {
			$ptgArea = pack("C", $this->ptg['ptgArea3dA']);
		} else {
			return $this->raiseError("Unknown class $class", 0, PEAR_ERROR_DIE);
		}

		return $ptgArea . $ext_ref . $row1 . $row2 . $col1. $col2;
	}

	/**
	* Convert an Excel reference such as A1, $B2, C$3 or $D$4 to a ptgRefV.
	*
	* @access private
	* @param string $cell An Excel cell reference
	* @return string The cell in packed() format with the corresponding ptg
	*/
	function _convertRef2d($cell)
	{
		$class = 2; // as far as I know, this is magick.

		// Convert the cell reference
		$cell_array = $this->_cellToPackedRowcol($cell);
		if (PEAR::isError($cell_array)) {
			return $cell_array;
		}
		list($row, $col) = $cell_array;

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgRef = pack("C", $this->ptg['ptgRef']);
		} elseif ($class == 1) {
			$ptgRef = pack("C", $this->ptg['ptgRefV']);
		} elseif ($class == 2) {
			$ptgRef = pack("C", $this->ptg['ptgRefA']);
		} else {
			// TODO: use real error codes
			return $this->raiseError("Unknown class $class");
		}
		return $ptgRef.$row.$col;
	}

	/**
	* Convert an Excel 3d reference such as "Sheet1!A1" or "Sheet1:Sheet2!A1" to a
	* ptgRef3d.
	*
	* @access private
	* @param string $cell An Excel cell reference
	* @return mixed The packed ptgRef3d token on success, PEAR_Error on failure.
	*/
	function _convertRef3d($cell)
	{
		$class = 2; // as far as I know, this is magick.

		// Split the ref at the ! symbol
		list($ext_ref, $cell) = split('!', $cell);

		// Convert the external reference part (different for BIFF8)
		if ($this->_BIFF_version == 0x0500) {
			$ext_ref = $this->_packExtRef($ext_ref);
			if (PEAR::isError($ext_ref)) {
				return $ext_ref;
			}
		} elseif ($this->_BIFF_version == 0x0600) {
			$ext_ref = $this->_getRefIndex($ext_ref);
			if (PEAR::isError($ext_ref)) {
				return $ext_ref;
			}
		}

		// Convert the cell reference part
		list($row, $col) = $this->_cellToPackedRowcol($cell);

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgRef = pack("C", $this->ptg['ptgRef3d']);
		} elseif ($class == 1) {
			$ptgRef = pack("C", $this->ptg['ptgRef3dV']);
		} elseif ($class == 2) {
			$ptgRef = pack("C", $this->ptg['ptgRef3dA']);
		} else {
			return $this->raiseError("Unknown class $class", 0, PEAR_ERROR_DIE);
		}

		return $ptgRef . $ext_ref. $row . $col;
	}

	/**
	* Convert the sheet name part of an external reference, for example "Sheet1" or
	* "Sheet1:Sheet2", to a packed structure.
	*
	* @access private
	* @param string $ext_ref The name of the external reference
	* @return string The reference index in packed() format
	*/
	function _packExtRef($ext_ref)
	{
		$ext_ref = preg_replace("/^'/", '', $ext_ref); // Remove leading  ' if any.
		$ext_ref = preg_replace("/'$/", '', $ext_ref); // Remove trailing ' if any.

		// Check if there is a sheet range eg., Sheet1:Sheet2.
		if (preg_match("/:/", $ext_ref)) {
			list($sheet_name1, $sheet_name2) = split(':', $ext_ref);

			$sheet1 = $this->_getSheetIndex($sheet_name1);
			if ($sheet1 == -1) {
				return $this->raiseError("Unknown sheet name $sheet_name1 in formula");
			}
			$sheet2 = $this->_getSheetIndex($sheet_name2);
			if ($sheet2 == -1) {
				return $this->raiseError("Unknown sheet name $sheet_name2 in formula");
			}

			// Reverse max and min sheet numbers if necessary
			if ($sheet1 > $sheet2) {
				list($sheet1, $sheet2) = array($sheet2, $sheet1);
			}
		} else { // Single sheet name only.
			$sheet1 = $this->_getSheetIndex($ext_ref);
			if ($sheet1 == -1) {
				return $this->raiseError("Unknown sheet name $ext_ref in formula");
			}
			$sheet2 = $sheet1;
		}

		// References are stored relative to 0xFFFF.
		$offset = -1 - $sheet1;

		return pack('vdvv', $offset, 0x00, $sheet1, $sheet2);
	}

	/**
	* Look up the REF index that corresponds to an external sheet name
	* (or range). If it doesn't exist yet add it to the workbook's references
	* array. It assumes all sheet names given must exist.
	*
	* @access private
	* @param string $ext_ref The name of the external reference
	* @return mixed The reference index in packed() format on success,
	*			   PEAR_Error on failure
	*/
	function _getRefIndex($ext_ref)
	{
		$ext_ref = preg_replace("/^'/", '', $ext_ref); // Remove leading  ' if any.
		$ext_ref = preg_replace("/'$/", '', $ext_ref); // Remove trailing ' if any.

		// Check if there is a sheet range eg., Sheet1:Sheet2.
		if (preg_match("/:/", $ext_ref)) {
			list($sheet_name1, $sheet_name2) = split(':', $ext_ref);

			$sheet1 = $this->_getSheetIndex($sheet_name1);
			if ($sheet1 == -1) {
				return $this->raiseError("Unknown sheet name $sheet_name1 in formula");
			}
			$sheet2 = $this->_getSheetIndex($sheet_name2);
			if ($sheet2 == -1) {
				return $this->raiseError("Unknown sheet name $sheet_name2 in formula");
			}

			// Reverse max and min sheet numbers if necessary
			if ($sheet1 > $sheet2) {
				list($sheet1, $sheet2) = array($sheet2, $sheet1);
			}
		} else { // Single sheet name only.
			$sheet1 = $this->_getSheetIndex($ext_ref);
			if ($sheet1 == -1) {
				return $this->raiseError("Unknown sheet name $ext_ref in formula");
			}
			$sheet2 = $sheet1;
		}

		// assume all references belong to this document
		$supbook_index = 0x00;
		$ref = pack('vvv', $supbook_index, $sheet1, $sheet2);
		$total_references = count($this->_references);
		$index = -1;
		for ($i = 0; $i < $total_references; $i++) {
			if ($ref == $this->_references[$i]) {
				$index = $i;
				break;
			}
		}
		// if REF was not found add it to references array
		if ($index == -1) {
			$this->_references[$total_references] = $ref;
			$index = $total_references;
		}

		return pack('v', $index);
	}

	/**
	* Look up the index that corresponds to an external sheet name. The hash of
	* sheet names is updated by the addworksheet() method of the
	* Spreadsheet_Excel_Writer_Workbook class.
	*
	* @access private
	* @return integer The sheet index, -1 if the sheet was not found
	*/
	function _getSheetIndex($sheet_name)
	{
		if (!isset($this->_ext_sheets[$sheet_name])) {
			return -1;
		} else {
			return $this->_ext_sheets[$sheet_name];
		}
	}

	/**
	* This method is used to update the array of sheet names. It is
	* called by the addWorksheet() method of the
	* Spreadsheet_Excel_Writer_Workbook class.
	*
	* @access public
	* @see Spreadsheet_Excel_Writer_Workbook::addWorksheet()
	* @param string  $name  The name of the worksheet being added
	* @param integer $index The index of the worksheet being added
	*/
	function setExtSheet($name, $index)
	{
		$this->_ext_sheets[$name] = $index;
	}

	/**
	* pack() row and column into the required 3 or 4 byte format.
	*
	* @access private
	* @param string $cell The Excel cell reference to be packed
	* @return array Array containing the row and column in packed() format
	*/
	function _cellToPackedRowcol($cell)
	{
		$cell = strtoupper($cell);
		list($row, $col, $row_rel, $col_rel) = $this->_cellToRowcol($cell);
		if ($col >= 256) {
			return $this->raiseError("Column in: $cell greater than 255");
		}
		// FIXME: change for BIFF8
		if ($row >= 16384) {
			return $this->raiseError("Row in: $cell greater than 16384 ");
		}

		// Set the high bits to indicate if row or col are relative.
		if ($this->_BIFF_version == 0x0500) {
			$row	|= $col_rel << 14;
			$row	|= $row_rel << 15;
			$col	 = pack('C', $col);
		} elseif ($this->_BIFF_version == 0x0600) {
			$col	|= $col_rel << 14;
			$col	|= $row_rel << 15;
			$col	 = pack('v', $col);
		}
		$row	 = pack('v', $row);

		return array($row, $col);
	}

	/**
	* pack() row range into the required 3 or 4 byte format.
	* Just using maximum col/rows, which is probably not the correct solution
	*
	* @access private
	* @param string $range The Excel range to be packed
	* @return array Array containing (row1,col1,row2,col2) in packed() format
	*/
	function _rangeToPackedRange($range)
	{
		preg_match('/(\$)?(\d+)\:(\$)?(\d+)/', $range, $match);
		// return absolute rows if there is a $ in the ref
		$row1_rel = empty($match[1]) ? 1 : 0;
		$row1	 = $match[2];
		$row2_rel = empty($match[3]) ? 1 : 0;
		$row2	 = $match[4];
		// Convert 1-index to zero-index
		$row1--;
		$row2--;
		// Trick poor inocent Excel
		$col1 = 0;
		$col2 = 16383; // FIXME: maximum possible value for Excel 5 (change this!!!)

		// FIXME: this changes for BIFF8
		if (($row1 >= 16384) or ($row2 >= 16384)) {
			return $this->raiseError("Row in: $range greater than 16384 ");
		}

		// Set the high bits to indicate if rows are relative.
		if ($this->_BIFF_version == 0x0500) {
			$row1	|= $row1_rel << 14; // FIXME: probably a bug
			$row2	|= $row2_rel << 15;
			$col1	 = pack('C', $col1);
			$col2	 = pack('C', $col2);
		} elseif ($this->_BIFF_version == 0x0600) {
			$col1	|= $row1_rel << 15;
			$col2	|= $row2_rel << 15;
			$col1	 = pack('v', $col1);
			$col2	 = pack('v', $col2);
		}
		$row1	 = pack('v', $row1);
		$row2	 = pack('v', $row2);

		return array($row1, $col1, $row2, $col2);
	}

	/**
	* Convert an Excel cell reference such as A1 or $B2 or C$3 or $D$4 to a zero
	* indexed row and column number. Also returns two (0,1) values to indicate
	* whether the row or column are relative references.
	*
	* @access private
	* @param string $cell The Excel cell reference in A1 format.
	* @return array
	*/
	function _cellToRowcol($cell)
	{
		preg_match('/(\$)?([A-I]?[A-Z])(\$)?(\d+)/',$cell,$match);
		// return absolute column if there is a $ in the ref
		$col_rel = empty($match[1]) ? 1 : 0;
		$col_ref = $match[2];
		$row_rel = empty($match[3]) ? 1 : 0;
		$row	 = $match[4];

		// Convert base26 column string to a number.
		$expn   = strlen($col_ref) - 1;
		$col	= 0;
		$col_ref_length = strlen($col_ref);
		for ($i = 0; $i < $col_ref_length; $i++) {
			$col += (ord($col_ref{$i}) - ord('A') + 1) * pow(26, $expn);
			$expn--;
		}

		// Convert 1-index to zero-index
		$row--;
		$col--;

		return array($row, $col, $row_rel, $col_rel);
	}

	/**
	* Advance to the next valid token.
	*
	* @access private
	*/
	function _advance()
	{
		$i = $this->_current_char;
		$formula_length = strlen($this->_formula);
		// eat up white spaces
		if ($i < $formula_length) {
			while ($this->_formula{$i} == " ") {
				$i++;
			}

			if ($i < ($formula_length - 1)) {
				$this->_lookahead = $this->_formula{$i+1};
			}
			$token = '';
		}

		while ($i < $formula_length) {
			$token .= $this->_formula{$i};
			if ($i < ($formula_length - 1)) {
				$this->_lookahead = $this->_formula{$i+1};
			} else {
				$this->_lookahead = '';
			}

			if ($this->_match($token) != '') {
				//if ($i < strlen($this->_formula) - 1) {
				//	$this->_lookahead = $this->_formula{$i+1};
				//}
				$this->_current_char = $i + 1;
				$this->_current_token = $token;
				return 1;
			}

			if ($i < ($formula_length - 2)) {
				$this->_lookahead = $this->_formula{$i+2};
			} else { // if we run out of characters _lookahead becomes empty
				$this->_lookahead = '';
			}
			$i++;
		}
		//die("Lexical error ".$this->_current_char);
	}

	/**
	* Checks if it's a valid token.
	*
	* @access private
	* @param mixed $token The token to check.
	* @return mixed	   The checked token or false on failure
	*/
	function _match($token)
	{
		switch($token) {
			case SPREADSHEET_EXCEL_WRITER_ADD:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_SUB:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_MUL:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_DIV:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_OPEN:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_CLOSE:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_COMA:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_SEMICOLON:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_GT:
				if ($this->_lookahead == '=') { // it's a GE token
					break;
				}
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_LT:
				// it's a LE or a NE token
				if (($this->_lookahead == '=') or ($this->_lookahead == '>')) {
					break;
				}
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_GE:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_LE:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_EQ:
				return $token;
				break;
			case SPREADSHEET_EXCEL_WRITER_NE:
				return $token;
				break;
			default:
				// if it's a reference
				if (preg_match('/^\$?[A-Ia-i]?[A-Za-z]\$?[0-9]+$/',$token) and
				   !ereg("[0-9]",$this->_lookahead) and 
				   ($this->_lookahead != ':') and ($this->_lookahead != '.') and
				   ($this->_lookahead != '!'))
				{
					return $token;
				}
				// If it's an external reference (Sheet1!A1 or Sheet1:Sheet2!A1)
				elseif (preg_match("/^\w+(\:\w+)?\![A-Ia-i]?[A-Za-z][0-9]+$/u",$token) and
					   !ereg("[0-9]",$this->_lookahead) and
					   ($this->_lookahead != ':') and ($this->_lookahead != '.'))
				{
					return $token;
				}
				// If it's an external reference ('Sheet1'!A1 or 'Sheet1:Sheet2'!A1)
				elseif (preg_match("/^'[\w -]+(\:[\w -]+)?'\![A-Ia-i]?[A-Za-z][0-9]+$/u",$token) and
					   !ereg("[0-9]",$this->_lookahead) and
					   ($this->_lookahead != ':') and ($this->_lookahead != '.'))
				{
					return $token;
				}
				// if it's a range (A1:A2)
				elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+:(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$token) and 
					   !ereg("[0-9]",$this->_lookahead))
				{
					return $token;
				}
				// if it's a range (A1..A2)
				elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+\.\.(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$token) and 
					   !ereg("[0-9]",$this->_lookahead))
				{
					return $token;
				}
				// If it's an external range like Sheet1!A1 or Sheet1:Sheet2!A1:B2
				elseif (preg_match("/^\w+(\:\w+)?\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/u",$token) and
					   !ereg("[0-9]",$this->_lookahead))
				{
					return $token;
				}
				// If it's an external range like 'Sheet1'!A1 or 'Sheet1:Sheet2'!A1:B2
				elseif (preg_match("/^'[\w -]+(\:[\w -]+)?'\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/u",$token) and
					   !ereg("[0-9]",$this->_lookahead))
				{
					return $token;
				}
				// If it's a number (check that it's not a sheet name or range)
				elseif (is_numeric($token) and 
						(!is_numeric($token.$this->_lookahead) or ($this->_lookahead == '')) and
						($this->_lookahead != '!') and ($this->_lookahead != ':'))
				{
					return $token;
				}
				// If it's a string (of maximum 255 characters)
				elseif (ereg("^\"[^\"]{0,255}\"$",$token))
				{
					return $token;
				}
				// if it's a function call
				elseif (eregi("^[A-Z0-9\xc0-\xdc\.]+$",$token) and ($this->_lookahead == "("))
				{
					return $token;
				}
				return '';
		}
	}

	/**
	* The parsing method. It parses a formula.
	*
	* @access public
	* @param string $formula The formula to parse, without the initial equal
	*						sign (=).
	* @return mixed true on success, PEAR_Error on failure
	*/
	function parse($formula)
	{
		$this->_current_char = 0;
		$this->_formula	  = $formula;
		$this->_lookahead	= $formula{1};
		$this->_advance();
		$this->_parse_tree   = $this->_condition();
		if (PEAR::isError($this->_parse_tree)) {
			return $this->_parse_tree;
		}
		return true;
	}

	/**
	* It parses a condition. It assumes the following rule:
	* Cond -> Expr [(">" | "<") Expr]
	*
	* @access private
	* @return mixed The parsed ptg'd tree on success, PEAR_Error on failure
	*/
	function _condition()
	{
		$result = $this->_expression();
		if (PEAR::isError($result)) {
			return $result;
		}
		if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_LT) {
			$this->_advance();
			$result2 = $this->_expression();
			if (PEAR::isError($result2)) {
				return $result2;
			}
			$result = $this->_createTree('ptgLT', $result, $result2);
		} elseif ($this->_current_token == SPREADSHEET_EXCEL_WRITER_GT) {
			$this->_advance();
			$result2 = $this->_expression();
			if (PEAR::isError($result2)) {
				return $result2;
			}
			$result = $this->_createTree('ptgGT', $result, $result2);
		} elseif ($this->_current_token == SPREADSHEET_EXCEL_WRITER_LE) {
			$this->_advance();
			$result2 = $this->_expression();
			if (PEAR::isError($result2)) {
				return $result2;
			}
			$result = $this->_createTree('ptgLE', $result, $result2);
		} elseif ($this->_current_token == SPREADSHEET_EXCEL_WRITER_GE) {
			$this->_advance();
			$result2 = $this->_expression();
			if (PEAR::isError($result2)) {
				return $result2;
			}
			$result = $this->_createTree('ptgGE', $result, $result2);
		} elseif ($this->_current_token == SPREADSHEET_EXCEL_WRITER_EQ) {
			$this->_advance();
			$result2 = $this->_expression();
			if (PEAR::isError($result2)) {
				return $result2;
			}
			$result = $this->_createTree('ptgEQ', $result, $result2);
		} elseif ($this->_current_token == SPREADSHEET_EXCEL_WRITER_NE) {
			$this->_advance();
			$result2 = $this->_expression();
			if (PEAR::isError($result2)) {
				return $result2;
			}
			$result = $this->_createTree('ptgNE', $result, $result2);
		}
		return $result;
	}

	/**
	* It parses a expression. It assumes the following rule:
	* Expr -> Term [("+" | "-") Term]
	*	  -> "string"
	*	  -> "-" Term
	*
	* @access private
	* @return mixed The parsed ptg'd tree on success, PEAR_Error on failure
	*/
	function _expression()
	{
		// If it's a string return a string node
		if (ereg("^\"[^\"]{0,255}\"$", $this->_current_token)) {
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		} elseif ($this->_current_token == SPREADSHEET_EXCEL_WRITER_SUB) {
			// catch "-" Term
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgUminus', $result2, '');
			return $result;
		}
		$result = $this->_term();
		if (PEAR::isError($result)) {
			return $result;
		}
		while (($this->_current_token == SPREADSHEET_EXCEL_WRITER_ADD) or
			   ($this->_current_token == SPREADSHEET_EXCEL_WRITER_SUB)) {
		/**/
			if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_ADD) {
				$this->_advance();
				$result2 = $this->_term();
				if (PEAR::isError($result2)) {
					return $result2;
				}
				$result = $this->_createTree('ptgAdd', $result, $result2);
			} else {
				$this->_advance();
				$result2 = $this->_term();
				if (PEAR::isError($result2)) {
					return $result2;
				}
				$result = $this->_createTree('ptgSub', $result, $result2);
			}
		}
		return $result;
	}

	/**
	* This function just introduces a ptgParen element in the tree, so that Excel
	* doesn't get confused when working with a parenthesized formula afterwards.
	*
	* @access private
	* @see _fact()
	* @return array The parsed ptg'd tree
	*/
	function _parenthesizedExpression()
	{
		$result = $this->_createTree('ptgParen', $this->_expression(), '');
		return $result;
	}

	/**
	* It parses a term. It assumes the following rule:
	* Term -> Fact [("*" | "/") Fact]
	*
	* @access private
	* @return mixed The parsed ptg'd tree on success, PEAR_Error on failure
	*/
	function _term()
	{
		$result = $this->_fact();
		if (PEAR::isError($result)) {
			return $result;
		}
		while (($this->_current_token == SPREADSHEET_EXCEL_WRITER_MUL) or
			   ($this->_current_token == SPREADSHEET_EXCEL_WRITER_DIV)) {
		/**/
			if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_MUL) {
				$this->_advance();
				$result2 = $this->_fact();
				if (PEAR::isError($result2)) {
					return $result2;
				}
				$result = $this->_createTree('ptgMul', $result, $result2);
			} else {
				$this->_advance();
				$result2 = $this->_fact();
				if (PEAR::isError($result2)) {
					return $result2;
				}
				$result = $this->_createTree('ptgDiv', $result, $result2);
			}
		}
		return $result;
	}

	/**
	* It parses a factor. It assumes the following rule:
	* Fact -> ( Expr )
	*	   | CellRef
	*	   | CellRange
	*	   | Number
	*	   | Function
	*
	* @access private
	* @return mixed The parsed ptg'd tree on success, PEAR_Error on failure
	*/
	function _fact()
	{
		if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_OPEN) {
			$this->_advance();		 // eat the "("
			$result = $this->_parenthesizedExpression();
			if ($this->_current_token != SPREADSHEET_EXCEL_WRITER_CLOSE) {
				return $this->raiseError("')' token expected.");
			}
			$this->_advance();		 // eat the ")"
			return $result;
		}
		// if it's a reference
		if (preg_match('/^\$?[A-Ia-i]?[A-Za-z]\$?[0-9]+$/',$this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's an external reference (Sheet1!A1 or Sheet1:Sheet2!A1)
		elseif (preg_match("/^\w+(\:\w+)?\![A-Ia-i]?[A-Za-z][0-9]+$/u",$this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's an external reference ('Sheet1'!A1 or 'Sheet1:Sheet2'!A1)
		elseif (preg_match("/^'[\w -]+(\:[\w -]+)?'\![A-Ia-i]?[A-Za-z][0-9]+$/u",$this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// if it's a range
		elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+:(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$this->_current_token) or 
				preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+\.\.(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$this->_current_token))
		{
			$result = $this->_current_token;
			$this->_advance();
			return $result;
		}
		// If it's an external range (Sheet1!A1 or Sheet1!A1:B2)
		elseif (preg_match("/^\w+(\:\w+)?\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/u",$this->_current_token))
		{
			$result = $this->_current_token;
			$this->_advance();
			return $result;
		}
		// If it's an external range ('Sheet1'!A1 or 'Sheet1'!A1:B2)
		elseif (preg_match("/^'[\w -]+(\:[\w -]+)?'\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/u",$this->_current_token))
		{
			$result = $this->_current_token;
			$this->_advance();
			return $result;
		}
		elseif (is_numeric($this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// if it's a function call
		elseif (eregi("^[A-Z0-9\xc0-\xdc\.]+$",$this->_current_token))
		{
			$result = $this->_func();
			return $result;
		}
		return $this->raiseError("Syntax error: ".$this->_current_token.
								 ", lookahead: ".$this->_lookahead.
								 ", current char: ".$this->_current_char);
	}

	/**
	* It parses a function call. It assumes the following rule:
	* Func -> ( Expr [,Expr]* )
	*
	* @access private
	* @return mixed The parsed ptg'd tree on success, PEAR_Error on failure
	*/
	function _func()
	{
		$num_args = 0; // number of arguments received
		$function = strtoupper($this->_current_token);
		$result   = ''; // initialize result
		$this->_advance();
		$this->_advance();		 // eat the "("
		while ($this->_current_token != ')') {
		/**/
			if ($num_args > 0) {
				if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_COMA or
					$this->_current_token == SPREADSHEET_EXCEL_WRITER_SEMICOLON)
				{
					$this->_advance();  // eat the "," or ";"
				} else {
					return $this->raiseError("Syntax error: comma expected in ".
									  "function $function, arg #{$num_args}");
				}
				$result2 = $this->_condition();
				if (PEAR::isError($result2)) {
					return $result2;
				}
				$result = $this->_createTree('arg', $result, $result2);
			} else { // first argument
				$result2 = $this->_condition();
				if (PEAR::isError($result2)) {
					return $result2;
				}
				$result = $this->_createTree('arg', '', $result2);
			}
			$num_args++;
		}
		if (!isset($this->_functions[$function])) {
			return $this->raiseError("Function $function() doesn't exist");
		}
		$args = $this->_functions[$function][1];
		// If fixed number of args eg. TIME($i,$j,$k). Check that the number of args is valid.
		if (($args >= 0) and ($args != $num_args)) {
			return $this->raiseError("Incorrect number of arguments in function $function() ");
		}

		$result = $this->_createTree($function, $result, $num_args);
		$this->_advance();		 // eat the ")"
		return $result;
	}

	/**
	* Creates a tree. In fact an array which may have one or two arrays (sub-trees)
	* as elements.
	*
	* @access private
	* @param mixed $value The value of this node.
	* @param mixed $left  The left array (sub-tree) or a final node.
	* @param mixed $right The right array (sub-tree) or a final node.
	* @return array A tree
	*/
	function _createTree($value, $left, $right)
	{
		return array('value' => $value, 'left' => $left, 'right' => $right);
	}

	/**
	* Builds a string containing the tree in reverse polish notation (What you
	* would use in a HP calculator stack).
	* The following tree:
	*
	*	+
	*   / \
	*  2   3
	*
	* produces: "23+"
	*
	* The following tree:
	*
	*	+
	*   / \
	*  3   *
	*	 / \
	*	6   A1
	*
	* produces: "36A1*+"
	*
	* In fact all operands, functions, references, etc... are written as ptg's
	*
	* @access public
	* @param array $tree The optional tree to convert.
	* @return string The tree in reverse polish notation
	*/
	function toReversePolish($tree = array())
	{
		$polish = ""; // the string we are going to return
		if (empty($tree)) { // If it's the first call use _parse_tree
			$tree = $this->_parse_tree;
		}
		if (is_array($tree['left'])) {
			$converted_tree = $this->toReversePolish($tree['left']);
			if (PEAR::isError($converted_tree)) {
				return $converted_tree;
			}
			$polish .= $converted_tree;
		} elseif ($tree['left'] != '') { // It's a final node
			$converted_tree = $this->_convert($tree['left']);
			if (PEAR::isError($converted_tree)) {
				return $converted_tree;
			}
			$polish .= $converted_tree;
		}
		if (is_array($tree['right'])) {
			$converted_tree = $this->toReversePolish($tree['right']);
			if (PEAR::isError($converted_tree)) {
				return $converted_tree;
			}
			$polish .= $converted_tree;
		} elseif ($tree['right'] != '') { // It's a final node
			$converted_tree = $this->_convert($tree['right']);
			if (PEAR::isError($converted_tree)) {
				return $converted_tree;
			}
			$polish .= $converted_tree;
		}
		// if it's a function convert it here (so we can set it's arguments)
		if (preg_match("/^[A-Z0-9\xc0-\xdc\.]+$/",$tree['value']) and
			!preg_match('/^([A-Ia-i]?[A-Za-z])(\d+)$/',$tree['value']) and
			!preg_match("/^[A-Ia-i]?[A-Za-z](\d+)\.\.[A-Ia-i]?[A-Za-z](\d+)$/",$tree['value']) and
			!is_numeric($tree['value']) and
			!isset($this->ptg[$tree['value']]))
		{
			// left subtree for a function is always an array.
			if ($tree['left'] != '') {
				$left_tree = $this->toReversePolish($tree['left']);
			} else {
				$left_tree = '';
			}
			if (PEAR::isError($left_tree)) {
				return $left_tree;
			}
			// add it's left subtree and return.
			return $left_tree.$this->_convertFunction($tree['value'], $tree['right']);
		} else {
			$converted_tree = $this->_convert($tree['value']);
			if (PEAR::isError($converted_tree)) {
				return $converted_tree;
			}
		}
		$polish .= $converted_tree;
		return $polish;
	}
}
?>
